1. Field of the Invention
The present invention relates to a light diffusing member for a transmission screen for use in transmission projection televisions and the like, and an optical member and a transmission screen using the light diffusing member.
2. Background Art
Transmission projection televisions are display devices for enlarging and projecting images from light sources such as CRTs, liquid crystal projectors, or DLPs on a transmission screen. In such display devices, a light diffusing plate or the like for diffusing outgoing light is provided on the surface of the screen to reduce dazzling at the time of visual observation of the screen. Further, in order to reduce a deterioration in visibility of the projected image caused by external light-derived dazzling on the screen surface, an antireflection film is sometimes provided on the screen surface. As disclosed, for example, in Japanese Patent Laid-Open Nos. 295818/1999 and 28169/1995, the above light diffusing plate or antireflection film is prepared by incorporating transparent fine particles such as an organic filler in a resin constituting the light diffusing plate and the like. Further, a plate having both light diffusing effect and antireflection effect has been developed by allowing transparent fine particles to be projected on the surface of a resin to form concaves and convexes on the surface of a light diffusing plate.
The provision of a protective layer (also known as a hard coat layer) on the surface of the light diffusing plate for screen surface protection purposes, however, has posed a problem that the concaves and convexes on the surface of the light diffusing plate disappear making it impossible to attain the antireflection effect.
On the other hand, when an attempt is made to provide a protective layer in such a thickness that exhibits the antireflection effect, the thickness of the protective layer should be around the level of concaves and convexes on the surface of the light diffusing plate, that is, should be smaller than the particle diameter of the transparent fine particles, posing a problem that satisfactory surface protective effect cannot be attained.